do you intend to have the bumper chromed or will it be painted? if the latter now the ends are cut off why not make a 'skeleton' in steel wire and skin it with sheet steel? it can be whatever shape you want/need it to be that way. if the former the same applies just more care needs to be taken with the sheet metal and it'll need to be thicker sheet (which will have the bonus of allowing more grinding/fettling to get the shape right.
either way you don't need to make the ends you already have work when for a similar amount of effort it can be just what you envisaged it to be.
neil.